The light is allmost "overkill" during this days up here. You better catch the next plane
Its nice to have the sun back again, but you now me. I'm found of the darkest part of the year as well.
I use 100-400 mm because its almost no perspective distortion when I use 100 mm on this one. I dont have any adjustable panorama head on my tripod and I've ended up with the 100-400 set to 100mm as the most useful lense for this kind of work.
On this picture I use "semi" manual layers. Here I let the PS stitch them together in normal mode because my experience is that PS have often have big problems with skies(in advanced mode), spesially clear skies with no clouds. I also often find it more useful to let PS generate layers who I'm able adjust later in the process. So you see, I try to get some help from the merge function in PS. When I'm satisfied with the colortones, I flatten the images and remove any visible transitions between the pictures. If nessary. Sometimes its ok, sometimes the automatic function is really a long way out of target
I assume there is more useful programs to do this easier, but I find PS ok for me.
An important thing is to get rid of the perspective distortions who appear because of position of the lense according to the "swingpoint" of the head.
I belive thats a long answer to your question. Yes, its because of the minimum egde distortion. I also find it important to have min. 40% overlay between the pictures when shooting.
Well, its bedtime. I gone to try to be in position when the "blur hour" appear to morrow morning. For me, the best light last for approx. 10 min before its to bright again.